1. Field of the Invention
The present invention relates to a method and a device for cooling a high voltage transformer for a microwave oven, and more particularly to a method and a device for cooling a high voltage transformer for a microwave oven so as to rapidly remove heat generated from a coil and a core in the operation of the high voltage transformer, thereby improving performance and quality of the microwave oven and the high voltage transformer.
2. Description of the Related Art
Generally, high voltage transformers are used in electronic appliances for preparing food using a high frequency, such as microwave ovens. The high voltage transformer is a kind of a power feed unit, which heats a heater of a magnetron for generating high frequency microwave and simultaneously constitutes a half-wave voltage doubler circuit, thereby applying high voltage of 4,000V to the magnetron via a condenser so that the magnetron generates the high frequency microwave.
In a process for manufacturing the above-described high voltage transformer, in order to protect the high voltage transformer from vibration, noise and heat generated by a strong magnetic field occurring when voltage is applied to an input side of the high voltage transformer, an impregnation step, in which the high voltage transformer is impregnated with an impregnant such as varnish, must be performed.
In case the high voltage transformer is manufactured by passing through the aforementioned impregnation step, the process for manufacturing the high voltage transformer is complicated and consequently equipment for manufacturing the high voltage transformer is increased in size. Further, since, in the high voltage transformer manufactured by passing through the impregnation step, the heat generated from the coil is not conducted to the core or the outside, the high voltage transformer is disadvantageous that it is difficult to miniaturize.
The aforementioned high voltage transformer has anther problem. That is, fires frequently break out by the thermosetting of varnish due to the heat. Since the coil charged with electricity is exposed to the outside, the coil is always in danger of fires and electric shocks.
In order to solve such problems, the present inventor(s) filed a method for manufacturing a non-impregnated high voltage transformer. Hereinafter, this patent application will be described with reference to FIGS. 1 and 2.
A plurality of E-type and I-type cores 1 and 2 are continuously manufactured by punching a steel plate 100 using a press, and vertically stacked so that the stack structures of the E-type and I-type cores 1 and 2 have a designated height so as to correspond to a width of a hole of a bobbin 4 to be integrated therewith.
The stack structure of the E-type cores 1 is inserted into the holes of the bobbins 4, provided with coils 5 wound thereon. Then, a two component adhesive 7, which is rapidly cured at room temperature, is coated at a designated amount and thickness on the upper surface of a central supporting portion 1a of the stack structure of the E-type cores 1, and the stack structure of the I-type cores 2 is attached to the central portion 1a coated with the two component adhesive 7.
Contact portions between both external corners of the upper surfaces of both side supporting portions 1b of the stack structure of the E-type cores 1 and both edges of the lower surface of the stack structure of the I-type cores 2 are welded, and several portions along the outer circumferences of the stack structure of the E-type cores 1 and the stack structure of the I-type core 2 are welded, thereby forming several welding areas 8.
An anticorrosive is sprayed on the surfaces of the stack structures of the E-type and I-type cores 1 and 2 and the exposed welding areas 8, thereby forming a rustproof layer 3. Embossed segments 6a or rivets 6b are used to fix the stack structures of the E-type and I-type cores 1 and 2 so as to form one block, thereby manufacturing a high voltage transformer.
As described above, the process for manufacturing the high voltage transformer without an impregnation step reduces a number of steps, improves productivity of the high voltage transformer, reduces the production cost of the high voltage transformer, and increases quality of the high voltage transformer due to the reduction of vibration and noise generation.
Insulation papers 10 are disposed along the outer surfaces of the coils 5 contacting the stack structures of the E-type cores 1 and I-type cores 2, thereby conducting the heat generated from the coil 5 to the core.
In the above-described conventional high voltage transformer, the insulation papers are used to conduct the heat generated from the coil to the core. However, since the heat generated from the coil is conducted to the core only via the insulation papers, a sufficient cooling rate by the heat conduction is not expected.
That is, the heat generated from the coil is conducted to the core via the insulation papers, and the heated core is cooled by means of a blast fan serving to forcibly cool the heat. However, since a portion of the high voltage transformer mounted on an external device is sealed, the cooling effect due to the forcible cooling using the blast fan is weak.
Particularly, since the high voltage transformer is not sealed but exposed to the outside when the high voltage transformer is mounted on the external device, the high voltage transformer exposes to a user to several dangers, such as an electrical shock, thereby being poor in terms of safety.